build: find dependencies for Go executables

To ensure that changing a dependency source file actually triggers
a rebuild of the core binaries when you type 'make', find their
dependencies and add them to the makefile's target dependencies.

Signed-off-by: Dan Williams <dcbw@redhat.com>

Makefile

@@ -68,15 +68,15 @@ copyimg: .gopathok $(wildcard test/copyimg/*.go)
 checkseccomp: .gopathok $(wildcard test/checkseccomp/*.go)
 	go build -o test/checkseccomp/$@ $(PROJECT)/test/checkseccomp
 
-ocid: .gopathok
+ocid: .gopathok $(shell hack/find-godeps.sh $(GOPKGDIR) cmd/ocid $(PROJECT))
 	$(GO) build -o $@ \
 		-tags "$(BUILDTAGS)" \
 		$(PROJECT)/cmd/ocid
 
-ocic: .gopathok
+ocic: .gopathok $(shell hack/find-godeps.sh $(GOPKGDIR) cmd/ocic $(PROJECT))
 	$(GO) build -o $@ $(PROJECT)/cmd/ocic
 
-kpod: .gopathok
+kpod: .gopathok $(shell hack/find-godeps.sh $(GOPKGDIR) cmd/kpod $(PROJECT))
 	$(GO) build -o $@ $(PROJECT)/cmd/kpod
 
 ocid.conf: ocid

hack/find-godeps.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+#
+# $1 - base path of the source tree
+# $2 - subpath under $1 to find *.go dependencies for
+# $3 - package name (eg, github.com/organization/project)
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+# might be called from makefile before basepath is set up; just return
+# empty deps.  The make target will then ensure that GOPATH is set up
+# correctly, and go build will build everything the first time around
+# anyway.  Next time we get here everything will be fine.
+if [ ! -d "$1/$2" ]; then
+	exit 0
+fi
+
+function find-deps() {
+	local basepath=$1
+	local srcdir=$2
+	local pkgname=$3
+	local deps=
+
+	# gather imports from cri-o
+	pkgs=$(cd ${basepath}/${srcdir} && go list -f "{{.Imports}}" . | tr ' ' '\n' | grep -v "/vendor/" | grep ${pkgname} | sed -e "s|${pkgname}/||g")
+
+	# add each Go import's sources to the deps list,
+	# and recursively get that imports's imports too
+	for dep in ${pkgs}; do
+		deps+="$(ls ${basepath}/${dep}/*.go | sed -e "s|${basepath}/||g") "
+		# add deps of this package too
+		deps+="$(find-deps ${basepath} ${dep} ${pkgname}) "
+	done
+
+	echo "${deps}" | sort | uniq
+}
+
+# add Go sources from the current package at the end
+echo "$(find-deps "$1" "$2" "$3" | xargs) $(cd $1 && ls $2/*.go | xargs)"
+